A liquid crystal display (LCD) assembly generally includes a glass LCD panel, a backlight system, and LCD driver electronics. The display assembly may also include an interface card to convert an analog or digital video signal (such as digital video interface or DVI) into another form such as low-voltage differential signaling (LVDS). Typical advantages of LCD technology over cathode-ray tube (CRT) technology include a smaller size and less weight for a similar display area.
FIG. 1A shows a cross-section of a display assembly including an LCD panel A5 and a light guide A6 edge-lit by one or more light sources A1 such as light-emitting diodes (LEDs) and/or fluorescent lamps. FIG. 1B shows a cross-section of an LCD with several light sources (such as cold-cathode fluorescent lamps or CCFLs) arranged as a curtain backlight.
Operating environments for LCD assemblies may be limited in temperature due to the nature of the liquid crystal (LC) technology. Above a particular temperature, the LC molecules become randomly or chaotically oriented, rather than being aligned according to the applied electric field. At high temperatures, therefore, a current state-of-the-art large-size LCD panel (for example, a panel having a diagonal dimension of 17 inches or larger) will become opaque, yielding a black display regardless of the state of the driving signal. This phenomenon, called “clearing” of the panel, is temporary and nondestructive, but it limits use of the panel to within certain temperature limits.
In recent years, it has become common for LCD panels to include liquid crystal materials having lower viscosities than before (e.g., by using additives). Panels using such mixtures tend to have faster response times, but the lower viscosities may also contribute to lower clearing temperatures.
Although LCD technologies capable of operating in higher-temperature environments exist, they are commercially available only in smaller-size displays and have other disadvantages such as longer rise and fall times, which results in poor representation of live video footage. At the other end of the temperature spectrum (e.g., at temperatures below 0° C.), the response of the LCD becomes very slow. In extreme cases the LCD material can freeze. While these effects may also be nondestructive, they limit the use of LCD technology in extreme temperature environments.